Hi there!
I don't have a Vespa gts250, nor am I a mechanic.... But I had a look at the workshop manual out of interest and there are some instructions and diagrams in there that should help heaps if you are doing the job yourself!!!
I tried downloading it from this website, but my Adobe Reader said the file was corrupt. Could be my computer, but I found a copy at this link: http://www.ebooksquad.com/2009/01/24/vespa-gts-250-workshop-manual.html Be aware the file is 14.92mb in size.....
Mind you, I've worked from manuals before and simple statements in the book like 'remove this' or 'unscrew that' take on a totally new meaning when faced with the actuality of getting to the part in question!!!! Sometimes I think the manuals have been written by people who have never seen the vehicle they are writing about, let alone done any work on them!
Nevertheless, good luck with your search.
With the very kindest regards
Live the Dream - Ride a Scoot!! Preferably a Daelim S1!!! Troy Corser knows how good these scoots are, cos he's got one!!!!!